unit tests coverage

Signed-off-by: Pujal <[email protected]>

Author: pujal0909

packages/zowe-explorer/__tests__/__mocks__/@zowe/imperative.ts

@@ -264,9 +264,9 @@ export class ImperativeError extends Error {
     public get details() {
         return this.mDetails;
     }
-    public get errorCode() {
-        return this.mDetails.errorCode;
-    }
+    // public get errorCode() {
+    //     return this.mDetails.errorCode;
+    // }
 }
 
 export class ProfInfoErr extends ImperativeError {

packages/zowe-explorer/__tests__/__unit__/trees/dataset/ZoweDatasetNode.unit.test.ts

@@ -1916,7 +1916,7 @@ describe("ZoweDatasetNode Unit Tests - listMembersInRange()", () => {
             contextOverride: Constants.DS_PDS_CONTEXT,
         });
 
-        jest.spyOn(pdsNode, "listMembers").mockRejectedValue(
+        jest.spyOn(pdsNode, "listMembers").mockRejectedValueOnce(
             new imperative.ImperativeError({
                 msg: "Dataset not cataloged",
                 errorCode: `${imperative.RestConstants.HTTP_STATUS_404}`,

packages/zowe-explorer/src/trees/dataset/ZoweDatasetNode.ts

@@ -834,10 +834,10 @@ export class ZoweDatasetNode extends ZoweTreeNode implements IZoweDatasetTreeNod
 
             await this.listMembers(responses, { attributes: true, start, maxLength: start ? limit + 1 : limit });
         } catch (err) {
-            if (Number(err.errorCode) === imperative.RestConstants.HTTP_STATUS_404) {
-                return {
-                    items: [],
-                };
+            if (err instanceof imperative.ImperativeError) {
+                if (Number(err.errorCode) === imperative.RestConstants.HTTP_STATUS_404) {
+                    return { items: [] };
+                }
             }
             const updated = await AuthUtils.errorHandling(err, {
                 apiType: ZoweExplorerApiType.Mvs,